The field of this invention relates to the welding of separate metallic cylindrical tubular elements. More particularly, this invention relates to a pipe welder to automatically efficiently produce an extremely strong weld between piping sections.
It has long been known that in the welding of any two parts together, a desirable type of weld is a weld bead which is slightly raised on both the interior and exterior surface of the parts. Satisfactory penetration of the heat energy must occur to melt the edges of the to be welded parts and then with the addition of a filler wire completely fill the welding groove with an intermolecular bond occurring between the melted filler wire and the metallic material of the parts.
The producing of a satisfactory weld requires a perfect or complete welding to occur along the entire length of the weld bead. If the two parts to be welded comprise a one foot diameter pipe, the actual weld bead in welding together the two pipes will be over three feet in length. A flaw of a fraction of an inch within that three feet of length will result in the producing of an unsatisfactory weld.
It has been common in the past to mount some form of track assembly on the pipe upon which is mounted a welding head assembly. The welding head assembly is movable around the track to automatically produce the weld which in turn will weld two sections of the pipe together. Because the production of an extremely high quality weld is required, any momentary pause or speeding up of the welding head will be sufficient to effect the quality of the weld. A pause can be created if only for a split second the driving mechanism, which moves the welding head, is disengaged from the track on which it is mounted. Therefore, it is exceedingly important that the driving mechanism be continuously and positively engaged with the track at all times it is operated to move the welding head on the track about the pipe.
Additionally, the mounting of a welding head onto a track is usually accomplished by means of some kind of a roller assembly in conjunction with a belt mounted about the pipe or a roller assembly in conjunction with a chain. Although such mountings of the welding head have been proved to be satisfactory in the past, there is a stringent requirement to produce such rollers, belts and chains with a high degree of tolerance so as to eliminate any pausing or speeding up of the welding head. However, with such types of welding head mounting devices, speeding up or pausing of the welding head does occur.
There is a need to positively mount the welding head onto the track so as to facilitate low frictional movement of the welding head about the track but also insure that the welding head will not vary even slightly in spacing from the surface of the pipe which is to be welded. Such variation in spacing will inherently cause the welding electrode to also vary which in turn will result in the production of a diminished quality weld. Therefore, it is exceedingly important that the welding head be attached to the track in such a manner as to not be movable radially outward therefrom as the welding head is moved around the track.
Additionally, it is important to have a welding head be as versatile as possible. At times it may be desirable to use only a single filler wire assembly, where at other times it may be more desirable to use a dual filler wire assembly. In the past, it has been common to construct welding apparatuses to utilize only a single filler wire assembly. It would be desirable to construct a welding head in which it would also be possible to use two in number of filler wire assemblies if such is found to be desirable for a particular welding situation.